This randomized controlled trial is intended to be the first in a series of trials that will assess the efficacy of drugs, which relieve neuropathic pain, on stimulus-evoked pain (here: mechanical hyperalgesia to static punctate stimuli). Most drugs in this class (e.g. Gabapentin or NMDA receptor inhibitors) have NNT beyond 3 in patients with chronic pain, due to a response rate of 30 to 50 %. One potential reason for this low overall efficacy might be the presence of different pathophysiological mechanisms in subgroups of patients, who suffer from the same disease (e.g. postherpetic neuralgia, diabetic neuropathy). These mechanisms may include central sensitization on one hand and peripheral degeneration of afferent fibers on the other hand.